This disclosure relates generally to the field of semiconductor manufacturing processes, and more specifically to cleaning of a deposition chamber used in a semiconductor manufacturing process.
Deposition processes may be used in semiconductor manufacturing to form a uniform layer of a material, such as a metal, a dielectric material, or a semiconducting material, on a substrate. The material may be deposited on the substrate using a plasma in a deposition chamber, which may be a vacuum chamber. Plasma tools used for deposition processes, such as chemical vapor deposition (CVD), sputtering, and so forth, may employ inductive coupling or capacitive coupling to strike and maintain the plasma in the deposition chamber. One advantage of inductively coupled plasmas is that they are generated with much smaller bias voltage on the substrate, reducing the likelihood of damage thereto. In addition, inductively coupled plasmas have a higher ion density, thereby providing higher deposition rates and mean free paths, while operating at a much lower pressure than capacitively coupled plasmas. These advantages allow in situ sputtering and/or ion directionality during processing.
High density plasma (HDP) CVD processes may be used to provide a combination of chemical reactions and physical sputtering. HDP-CVD processes promote the disassociation of the reactant gases by the application of radio frequency (RF) energy to the reaction zone proximate to the substrate surface, thereby creating a plasma of highly reactive ionic species. The relatively non-reactive ionic constituents, i.e., argon (Ar), are given high momentum (efield) to dislodge deposited film material selectively from specific areas along the profile of the film based on a sputter yield curve. The high reactivity of the released ionic species reduces the energy required for a chemical reaction to take place, thus lowering the required temperature for these processes.
The goal in most HDP-CVD processes is to deposit a film of uniform thickness across the surface of a substrate, while also providing good gap fill between lines and other features formed on the substrate. Deposition uniformity and gap via fill are very sensitive to source configuration, gas flow changes, source RF generator power, bias RF generator power, gas nozzle design, including symmetry in distribution of nozzles, the number of nozzles, the height of the nozzles above the substrate support, and the lateral position of the nozzles relative to the substrate support. These variables change and processes are performed within the tool change and as process gases change.
One problem encountered in semiconductor manufacturing is deposition of material on the deposition chamber itself during deposition on the substrate. During deposition, the material deposits not only on the substrate, but throughout the chamber interior, on the substrate support member (pedestal), and on the gas distribution components (shower head). Over time, built up material on the chamber interior may flake off into the chamber during subsequent processing of a substrate, resulting in particle contamination of the substrate, which can compromise the integrity of the device being fabricated. Thus, the chamber must be periodically cleaned to prevent particles issues by removing any films deposited on the pedestal, shower head, and chamber wall.
A CVD process may include a chamber clean after every deposition, while a metal sputtering chamber may be cleaned only after certain cycles. Standard deposition chamber cleaning processes may require multiple iterations of radiofrequency (RF) and remote plasma source (RPS) cleaning steps to thoroughly remove deposited material from the chamber interior. RF cleaning energizes gas plasma including ions, electrons, radicals, and metastables to remove the carbon or hydrocarbons in the film located on the chamber interior through a chemical reaction with an active gas, such as oxygen. RPS cleaning provides a gentler cleaning step to further clean around chamber areas including the showerhead. Many iterations of RF and RPS cleaning steps may be necessary in order to sufficiently clean the chamber, which may require a relatively long period of time for the cleaning process. During the cleaning process, the deposition chamber may not be used for device fabrication, which decreases throughput for the fabrication process.
After cleaning, the shower head and chamber wall may be coated with another film prior to subsequent deposition. This additional coating step, known as seasoning, is needed to prevent plasma damage to the chamber wall during subsequent deposition processes. The chamber clean process needs to effectively remove all residual films from the chamber before seasoning. In order to sufficiently clean all exposed chamber surfaces, the length of time allotted for the cleaning process may be increased, which increases idle time for the chamber and decreases throughput for the manufacturing process. The cleaning process may also be performed using higher temperatures, which may effectively overclean the chamber surfaces, and increase the cost of consumables and/or maintenance intervals for the tool. Switching chamber temperature for cleaning is usually not preferred by manufacturing since it requires additional time for chambers to stabilize after cleaning Also, excessive cleaning time and temperatures may be damaging to the deposition chamber.